Currently, turbine installations are subject to an overall inspection during which the entire turbine installation is generally shutdown in the basis of an empirical variable applicable to the entire turbine. During these downtimes, critical components of the turbine installation, such as the guide vanes and rotor blades or combustion chamber linings, for example, are inspected in more detail to determine whether the condition of the components permits further use of these components in the operation of the turbine installations or whether replacement or overhaul of the components may be necessary in order to prevent failure during the operation of the turbine installation.
By way of example, the effective operating hours (abbreviated EOH) can be the significant variable which governs the maintenance downtimes and is calculated using empirical formulae. The following input variables are conceivable: the operating hours (abbreviated OH) of the turbine installation, the so-called dynamic hours (abbreviated Dyn H), that is to say the operating hours during which the turbine installation is subject to large changes in the operating state (which are linked to large changes in the load, particularly thermal load changes on the components of the turbine installation), and the number of turbine initializations, are included.
It is conventional to carry out an inspection of a turbine installation after the course of a predetermined number of effective operating hours.
However, the influence of the actual load, the set turbine inlet temperature and the fuel are ignored in this known inspection method. Furthermore, a particular, component-specific finding progress, in the form of crack growth for example, is also not considered. The components of the turbine installation are usually only examined and no measures for possible repairs are derived on the basis of the undertaken inspection. The only components that can be and are also replaced within the course of inspections are ceramic and metallic heat shields, with the ceramic heat shields being replaced, if applicable, by means of an empirically set crack length criterion based on visual inspection, and, in this case, the life of the heat shields is not usually utilized to its full extent.
When taking everything into consideration, it should therefore firstly be noted that known inspection methods often do not utilize the life of the components of turbine installations optimally. Furthermore, the components are only examined during the downtimes provided for the overall inspection, so that possibly critically damaged components may not be identified at an early enough stage, which is linked to a risk during the operation of the turbine installation which cannot be ignored.
Furthermore, EP 1 227 222 A2 discloses a method for determining the time for servicing a gas turbine. The time for servicing is determined in this case as a function of the wear of a monitored turbine blade, with the wear of the turbine blade being determined by means of a temperature sensor.
Furthermore, DE 198 43 615 A1 discloses a servicing monitoring unit for calculating and displaying the due date of the next servicing of a combustion drive. The servicing monitoring unit in this case observes the temporal profiles of the actual values of operating signals or parts thereof (for example, the rotor rotational speed) and derives conclusions about an inspection being required soon.